| Low back pain (LBP) has been associated with pelvic and lower limb asymmetries, and with altered trunk motion. However, evidence of such associations remains equivocal. Given the lack of a pathoanatomic diagnosis for most LBP, I investigated the possibility of developing alternate LBP classifications using patterns of movement and structural asymmetries.; My thesis consists of four studies. In the first study, I measured fluctuating asymmetry (FA); i.e., random deviations from perfect symmetry in morphological bilateral traits, in 44 subjects with unilateral mechanical LBP and 51 controls. This study demonstrated a link between LBP and FA; an inverse measure of developmental stability. The LBP group exhibited greater pelvic asymmetry, as well as greater asymmetry in ulnar length and bistyloid breadth.; In the second study I developed an objective, non-invasive, and reliable measure of trunk motion, which I used in the next two studies to assess trunk lateral flexion and axial rotation. Using surface markers, the trunk was divided into four regions; each region considered a segment, and relative motion between adjacent segments was measured using local coordinate systems embedded in each segment. Subjects with LBP (n = 54) showed greater asymmetry in lumbar movement than asymptomatic controls (n = 59). While the groups had similar ranges of lumbar motion, the LBP group had reduced range of motion in the lower thoracic region. The LBP group also showed altered pattern of coupled movement (i.e., movement in a plane other than the principal motion executed by the subject). In both sitting and standing postures, restricted lumbar motion correlated with the specific type of pelvic asymmetry: lateral pelvic tilt and iliac rotation asymmetry.; Collectively, the final two studies demonstrated that a subtle anatomical abnormality in the pelvis is associated with altered mechanics in the lumbar spine in patients with LBP and asymptomatic controls. While clinicians often use the absolute range of lumbar motion to assess LBP patients, these results indicate that the pattern of asymmetry in lumbar movement may be a better indicator of functional deficits in the back. Pelvic asymmetry and asymmetrical trunk movements are of diagnostic value for people with unilateral LBP. |
